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Sequence of the M28 dsRNA: preprotoxin is processed to an alpha/beta heterodimeric protein toxin

M J Schmitt1, D J Tipper

  • 1Institut für Mikrobiologie und Weinforschung, Johannes Gutenberg-Universität Mainz, Germany.

Virology
|November 10, 1995
PubMed

Insights

The M28 virus in Saccharomyces cerevisiae encodes the K28 preprotoxin (M28p), responsible for killer and immunity traits. Its processing and secretion involve specific protein interactions and cellular machinery.

Area of Science:

  • Molecular Biology
  • Yeast Genetics
  • Virology

Background:

  • The K28 killer and immunity phenotypes in Saccharomyces cerevisiae are conferred by the M28 dsRNA virus.
  • The M28 virus encodes the K28 preprotoxin (M28p), a key determinant of these traits.

Purpose of the Study:

  • To elucidate the genetic basis and molecular mechanisms underlying the K28 killer toxin production and immunity in yeast.
  • To characterize the M28 preprotoxin gene and its role in conferring the killer phenotype.

Main Methods:

  • Analysis of the M28 dsRNA virus genome, focusing on the M28p gene sequence and its regulatory elements.
  • Investigating the role of M28p in conferring killer and immunity phenotypes through expression studies.
  • Examining the K28 toxin structure, including its alpha and beta components and their N-termini.
  • Assessing the impact of mutations in Kex2p and Kex1p on toxin secretion and activity.

Main Results:

  • The M28p gene (bases 13-1047) is located on the M28 dsRNA plus strand, followed by poly(A) and 3'-sequences involved in encapsidation.
  • Expression of M28p alone confers the complete K28 killer and immunity phenotype.
  • K28 toxin is a heterodimer of alpha and beta subunits, with N-termini derived from M28p.
  • Signal peptides influence toxin secretion, and Kex2p and Kex1p are involved in toxin processing, though alpha component cleavage requires further investigation.

Conclusions:

  • The M28 dsRNA virus and its M28p gene are sufficient to establish the K28 killer and immunity phenotypes in yeast.
  • The processing and secretion pathways for K28 toxin share similarities with other yeast toxins, despite sequence differences.
  • Understanding these mechanisms provides insight into viral toxin production and host-pathogen interactions in Saccharomyces cerevisiae.

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